Two metal wires of identical dimensions are connected in series. If σ1 and σ2
1. | 2σ1σ2σ1+σ2 | 2. | σ1+σ22σ1σ2 |
3. | σ1+σ2σ1σ2 | 4. | σ1σ2σ1+σ2 |
A potentiometer wire of length L and a resistance r are connected in series with a battery of EMF E0 and resistance r1. An unknown EMF is balanced at a length l of the potentiometer wire. The EMF E will be given by:
1. LE0rlr1
2. E0r(r+r1)⋅lL
3. E0lL
4. LE0r(r+r1)l
A potentiometer wire has a length of 4 m and resistance 8 Ω. The resistance that must be connected in series with the wire and an energy source of emf 2 V, so as to get a potential gradient of 1 mV per cm on the wire is:
1. 32 Ω
2. 40 Ω
3. 44 Ω
4. 48 Ω
A,B and C are voltmeters of resistance R, 1.5R and 3R respectively as shown in the figure above. When some potential difference is applied between X and Y, the voltmeter readings are VA, VB and VC respectively. Then:
1. | VA=VB=VC | 2. | VA≠VB=VC |
3. | VA=VB≠VC | 4. | VA≠VB≠VC |
1. | current density | 2. | current |
3. | drift velocity | 4. | electric field |
Two cities are 150 km apart. The electric power is sent from one city to another city through copper wires. The fall of potential per km is 8 volts and the average resistance per km is 0.5 ohm. The power loss in the wire is:
1. 19.2 W
2. 19.2 kW
3. 19.2 J
4. 12.2 kW
The figure given below shows a circuit when resistances in the two arms of the meter bridge are 5 Ω and R, respectively. When the resistance R is shunted with equal resistance, the new balance point is at 1.6l1. The resistance R is:
1. 10 Ω
2. 15 Ω
3. 20 Ω
4. 25 Ω
A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance, R, connected across the given cell, has values of (i) infinity (ii) 9.5, the 'balancing lengths, on the potentiometer wire, are found to be 3 m and 2.85 m, respectively. The value of the internal resistance of the cell is (in ohm):
1. 0.25
2. 0.95
3. 0.5
4. 0.75
A wire of resistance 4 Ω is stretched to twice its original length. The resistance of a stretched wire would be:
1. | 4 Ω | 2. | 8 Ω |
3. | 16 Ω | 4. | 2 Ω |